PLA Forums
OMG IT'S TEH PLA! => All Things PLA => Topic started by: rbcp on April 05, 2006, 02:49:30 PM
-
Comments on our cordless phone page. Which can be found here:
http://www.phonelosers.org/article/cordless/ (http://www.phonelosers.org/article/cordless/)
-
RBCP do you have the 800MHz channels ?
-
I was recently at a hamfest and picked up a device called a DTMF decoder. It basically hears a phone tone and tells you what number that was pressed, or if it was * or #. So one day I hear on my scanner and phone call, then ringing, then....
Welcome to Well Fargo phone banking. Please enter you 9 digit account number: then I hear the beep, bop, boop, berp, bomp of the numbers being pressed.
Then I hear: Thank you. Please hold while we access your account
Then I hear: Please enter you pass code and again: boop, beep, berp etc
Then I hear: You account balance is six thousand, two hundred, and sixty eight dollars etc
To transfer funds to another account press 1
To hear your most recently cleared checks, press 2
To inquire on another account press 3. etc
Hmmmmm. It's lucky for them that I'm not a crook
-
You could stand to be a little more subtle while advertising your newness to this place.
-
RBCP do you have the 800MHz channels ?
The trick is just to scan the frequency band. Channels vary from phone to phone. Most 900 MHz phones are heard between 902 and 928 MHz.
-
What a sad lot ! Try getting out of the house and get a life !
-
Most 900MHz analog cordless phones seem to be using 30kHz spacing and WFM (wide FM) so don't scan using the 12.5kHz steps that you'd typically use on frequencies near that range for NFM (narrow FM) public service band stations. Scanning with a 10kHz tuning step should yield good results. If you don't have a wide FM bandwidth setting on your scanner, the phones will sound loud and distorted, especially the handsets themselves. The louder the person talks, the worse it sounds.
Many phones are digital or even spread spectrum which you can't listen to however with the popularity of Wal=Mart el cheapo phones there are a heck of a lot of new analog phones out there. 49MHz not so much anymore, but still plenty of analog 900MHz and analog 2.4GHz to listen to. Wait, how do you listen to analog 2.4GHz phones unless you have a super 1337 expensive scanner? Well back in the day someone had the bright idea of offering cable TV services wirelessly. This service was called MMDS and transmitted analog cable TV channels over the air on a frequency normal TV's couldn't receive, you guessed it, right around 2.4GHz. A home user would be supplied with an antenna and a downconverter which would allow their TV to pick up signals at that high of a frequency. Now that digital cable and minidish satellites rule the market, most MMDS systems have been taken down and there's loads of obsoleted surplus MMDS equipment out there, a lot of it residing on eBay for cheap. You can use this same equipment to downconvert the 2.4GHz cordless phone band down to a frequency any old scanner can pick up. Many convert to 140MHz or thereabouts or around 450MHz. The downconverters were typically powered via the TV coax line so you'll need to build or buy a power injector. They're very easy to make, or you could even rob one from an old Radio Shack mast mount TV antenna amplifier. One could be improvised out of a TV splitter, a DC block and a 12VDC (or 18V depending on the model) wall transformer. Some downconverters have an integrated antenna, like the ones assembled into a BBQ grill looking antenna. Keep the BBQ reflector for some great gain, directionality and range, or ditch it and use just the downconverter with its built in antenna for portability. Some you have to hook an antenna up to it. You could make one, or use one made for a wireless LAN since they're the same frequency. Transmissions are wide FM just like the 900MHz ones. For the record, these things tend to be a lot more sensitive than the 1337 expensive scanners that actually dial in to 2.4GHz. Difference is that your investment here will be around $10 versus $500+. Cordless phone listening dying? No, we're just having to get a little more creative, that's all!